Friction material

ABSTRACT

The friction material consists of a mixture of chromic oxide and 5 to 25 of zirconium oxide. At least a third oxide such as neodymium oxide may be added to the mixture and known lubricants such as graphite, molybdenum bisulfide, calcium or barium fluoride may also be added to the mixture.

United States Patent [191 Courcier et al.

FRICTION MATERIAL Assignee: Commissariat a IEnergie Atomique,

Paris, France Filed: July 13, 1971 Appl. No.: 162,215

Related U.S. Application Data Continuation-impart of Ser. No. 829,248, June 2, I969. abandoned.

Foreign Application Priority Data June 27, 1968 France 68.15677Z US. Cl. LI....IITIII.TLT T TEHT Int. Cl Cl0m 7/02 Field of Search 252/12, 12.2, 12.4, 12.6

[ June 11, 1974 [56] References Cited UNITED STATES PATENTS 3,573,204 3/l97l Van Wyk 252/12 3,652,408 3/1972 Korshak et al 252/12 Primary Examiner-Daniel E. Wyman Assistant Examinerl. Vaughn Attorney, Agent, or FirmCameron, Kerkam, Sutton, Stowell & Stowell [5 7 ABSTRACT The friction material consists of a mixture of chromic oxide and 5 to 25 of zirconium oxide. At least a third oxide such as neodymium oxide may be added to the mixture and known lubricants such as graphite, molybdenum bisulfide, calcium or barium fluoride may also be added to the mixture.

1 Claim, 1 Drawing Figure PATENTEDJUN 1 1 I914 38 16309 COEFFICIENT 1= FRICTION x 10' WEAIQ 1N GRAM5 x 40 I l l l- FRICTION 30 K \v \(/WEAR 1o 10 2o 40 60. 90100 FCnzQg'INTHE MIXTURBOF Cn2O +ZnO 3 ,8 1 6,309 1 2 FRICTION MATERIAL part or in the form of a coating. In the first case, any

REFERENCE To RELATED APPLICATION powder metallurgy technique may be adopted for the formation of such solid parts. In the second case, re-

This application is a continuation-in-part of our apcourse may be had to techniques such as oxide coating plication Ser. No. 829,248, filed June 2, 1969, for Fric- 5 or metallic coating followed by application of oxides. tion Material, which application is abandoned. In particular, it is of interest to employ ordinary flame- The present invention relates to a novel friction maspray processes or plasma-spray processes. The sprayterial, especially for dry friction, which is more espegun can be fed with material in either powder or rod cially adapted to constitute a surface coating for parts form, the oxides being first mixed together or sprayed in relative motion. at the same time. The plasma-spray gun (jet) can be fed It is known that some particular environments such with oxides either in the pure or mixed state. In particuas high-temperature media, nuclear media, corrosive lar, it is thus possible to apply a thin coating of the atmospheres, high vacua and the like can call for the oxide mixture to the part to be coated by spraying with use of appliances or mechanisms constructed by means the plasma jet a fine powder having a particle size beof parts formed of special materials. It is also known tween 10 and microns at a rate of l/min. of argon that the atmospheres in which such appliances are and a power of 2] kW (700 amps 30 volts). caused to operate do not permit the use of conven- The table given below by way of indication summartional lubricants in the majority of cases. izes a number of tests carried out on parts and espe- The present invention is directed to a novel material cially on a journal mounted in a journal-bearing, the which meets the above-mentioned requirements and 2() material which constitutes said parts being provided or permits dry friction of moving parts with appreciable not provided with a surface coating in accordance with reduction of wear of these latter and a substantial rethe invention. Results of tests carried out under the folduction of the dangers of seizure. lowing conditions: Dry friction, load of 30 decanew- To this end said material is characterizedin that it tons, linear speed 0.14 m/sec.

Total weight loss during testing of- Coeflicient of Duration of Journal, Bearing, Nature oi journal material Nature of bearing material iriction test in hours in grams in grams Remarks Stainless steel Stainless steel 0. 9 0 hr. 32 mius i. 45 0. 13 Violent seizure. Chrome stainless steel Chrome stainless steel-.. 0. 85 0 hr. 45 mins 1. 52 0. 011 Very rapid wear ol iournal. CnO- GU03. 0. 3 46 hrs.... 0. 06 0. 07 Rapid wear and seizure. Zi-Oa Zl'Os- 1 0.30 0.07 Seizure. Mixture CnOrZrOQ (15%)- Cn0; 0. 04 0. 04 Very low wear.

is made up of a mixture of chromic oxide and zirco- In addition, the following results have been obtained nium s e n va blsareae ie t re a y th Ps 9". a fastiesraab a h amperage, yasuwwm;

Coefi. of

Speed, Duration trie- Pair of materials Load m./see. Atmosphere of test tion Remarks :::::}500 Newtons- 0. 14 3Xl0- torr at 500 0---. 1 hr 0.8 Very stable ooeflicient. Little wear. No seizure.

centage of zirconium oxide in the initial mixture is By way of explanatory illustration, the single FIG- comprised between 5 and 25 percent. URE of the accompanying drawings relates to tests on A reduction in the weight percentage of the zircocontinuous coatings of mixtures of chromic oxide'with nium oxide leads to an increase in wear and in the coefzirconium oxide in variable proportions. The curves ficient of friction. Similarly, an excessive increase in 5 which are plotted relate to wear and to the coefficient the weight percentage of zirconium oxide also gives rise of friction in ambient air of a journal formed of nitrided to the same disadvantages. However, within the weight steel and coated with a mixture of chromic oxide and limits mentioned above, experience has shown that a zirconia having a thickness of 2/10 mm on a bearinggreater degree of stability and regularity of the coefficiblock formed of the same steel and coated with pure ent of friction are obtained with the highest percent- 55 chromic oxide.

ages of zirconium oxide. This material very readily per- The parts are placed in contact with each other and mits incorporation of additives which have known luloaded prior to setting the machine in operation. The

bricating properties such as graphite, molybdenum machine is stopped 3 hours after start-up. The journal bisulphiade, calcium fluoride or barium fluoride which i and the bearing remain in contact and under load for are subsequently incorporated in the material. Morea period of 1 hour. At the end of this period, the maover, it has been observed experimentally that an imchine is again started up for a further cycle which lasts provement in the qualities of the friction material could 1 hours. W

be achieved by adding at least a third oxide to the mix- 1. Friction material consisting essentially of a mixture ture of chromic oxide and zirconium oxide. Advantaof chromic oxide and zirconium oxide the percentage geously, this third oxide is neodymium oxide. ,5 of zirconium oxide in the mixture of chromic oxide and The friction material under consideration can be uti- V zirconium oxide being from about 5 to about 25 perlized in two forms, namely either in the form of a solid cent. 

